1. Field of the Invention
This invention relates to tools that are operable through a power unit and, more particularly, to a control for selectively changing the state of the power unit.
2. Background Art
A wide range of power operated, portable tools are currently available for use in a wide range of environments. An exemplary tool construction employs a power unit that is either gas or electrically operated. The user supports the tool in an elevated, operating position through the use of spaced handles.
It is also known to construct such power tools using a "backpack" construction. This is a common configuration for commercial blower units. The frame carrying the power unit and other operating components is supported on user's back, thereby freeing both of the user's hands to operate controls for the power unit and appropriately orient an air discharge fitting.
To permit the user to control the back mounted power unit, it is known to project an operating arm on the frame to forwardly of the user's body and to locate and operate one or more actuators at the free end thereof. Typically, the arm projects forwardly and angularly outwardly between the user's torso and arm so that the actuator(s) at the free end can be accessed with the user's arm in a relatively comfortable orientation.
The arm carrying the actuator(s) is typically rigid and mounted movably to the frame to allow repositioning of the actuator(s) on the arm to suit the preference of the user. One typical mounting has a horizontal and laterally extending pivot point which results in the arm's tracing a conical surface as it is repositioned. This arm construction has been operatively effective, but has a number of drawbacks.
First of all, the available orientations of the actuator(s) at the end of the arm are limited. A predetermined angular relationship between the arm and the frame may not place the actuator(s) in the optimum position for all body sizes.
Further, this arm is prone to hanging up on vegetation and other objects around which the tool is commonly used. In use, the angularly oriented arm, in conjunction with the frame and the user's body, create a forwardly opening "V" shape which tends to funnel objects encountered into an entangled position at the base of the "V". Aside from the obvious inconvenience, this condition is potentially dangerous in that the user may, as result, become unbalanced and may fall and sustain an injury.
A further problem with this arm construction is that it is prone to breakage. The pivot connection gives the arm one degree of freedom. However, an impact imparted to the arm of a certain magnitude and in a certain direction may cause the arm to bend or break. Crews using this type of equipment often carelessly throw the tool into a flatbed vehicle commonly used in landscaping operations. If the initial drop of the power tool does not damage the arm, the tool might also shift during transportation as would have the same detrimental effect.
Aside from the potential damage to the arm, depending upon the construction of the actuator(s) at the end thereof and the attaching mechanism, the actuator(s) and/or the frame of the power tool may also be damaged through such impact.